Twin-tunnel kiln and method of operating the same



July 1, 1924. 1,499,354

C. DRESSLER TWIN TUNNEL KILN AND METHOD OF OPERATING THE SAME Filed June 14, 1923 2 sheets-sheet 1 INVENTOR ATTORNEY Juiy 1 1924.

c. DRESSLER TWIN TUNNEL KILN AND METHOD OF OPERATING THE SAME Filed June 14, 1923 2 Sheets-Sheet 2 INVENTOR Wm 5mm ATTORNEY Patented July 1, 1924. v

UNITE STATES orrics.

CONRAD DRES SLER, OF CLEVELAND, OHIO, ASSIGNOB TO AMERICAN DRESSLEB TUN- NEL KILNS, INC., 0]? CLEVELAND, OHIO, A CORPORATION OF NEW YORK.

TWIN-TUNN EL KILN AND METHOD OPERATING THE SAME.

Application filed June 14, 1928. Serial No. 645,307.

To all whom it may concern:

Be it known that I, CONRAD DRESSLER, a subject of the King of Great Britain, and resident of Cleveland, in the county of Cuyahoga and State of Ohio, have invented certain new and useful Improvements Pertaining to Twin-Tunnel Kilns and Methods of Operating the Same, of which the following is a specification.

My present invention relates to the socalled twin tunnel kilns, in which the ware treated passes in two sideby side streams traveling in opposite directions through the kiln chamber to which heat is imparted in a portion of the kiln intermediate its ends, so that as the ware in each stream approaches the high temperature'zone of the kiln it receives heat from the adjacent ware in the other stream which is thereby cooled.

The object of the invention is to improve the manner in which heat is transferred in 'a twin kiln from the hotter outgoing ware in the one' stream, to the cooler incoming were in the other stream. To. accomplish this-result, I provide means for maintaining a forced circulation of the kiln atmosphere along paths generally transverse to .the length of the kiln. Preferably the circulation inducing means employed augment the natural, or convection circulation of the kiln atmosphere across the goods from the hotter goods to the cooler goods at the top of'the kiln chamber, and from the cooler I goods to the hotter goods at the bottom of the kiln chamber. Ordinarily the circulation is best obtained by injecting suitably directed jets of a gaseous medium into the kiln chamber at appropriate points along the length of the kiln. The gaseous medium thus injected may well be cold air in many cases since the volume of the air introduced into the kiln by the jets need not be large enough to appreciably unduly cool the kiln, or otherwise objectionabl affect conditions in the kiln chamber. 0 avoid any kiln cooling efiect by the gaseous medium injected, the medium may be preliminarily heated or may consist of a combustible gas, or a mixture of combustible gas and air for its combustion, which ignites on its admission to the kiln chamber, and thus not only avoids cooling but. may actually impart heat to the kiln. In lieu of the gaseous mediums mentioned above 1 may induce the desired kiln circulation with other gaseous mediums such as products of combustion when this is convenient or desirable to maintain a particular character of kiln chamber in which the increased circulation is most needed are too high to permit the effective practical use of such fans.

When air or other gaseous medium is injected into the kiln chamber to effect the desired forced circulation, a corresponding portion of the kiln atmos here must be allowed to escape from the 'ln chamber. For this purpose special provisions are required with some types of kilns. These provisions may comprise suitable outlets from the kiln chamber adjacent its ends, though the outlets may be located adjacent the kiln center in some cases. The invention is usefiil alike with mullle' heated kilns and electrically heated kilns and with kilns, such as regenerative and other kilns, in which the heating gases pass through the high temperature portion of the kiln chamber in direct contact with the ward.

The various features of novelty which characterize my invention are pointed out with articularity in-the claims annexed to and orming a part of this specification. For a better understanding of the invention, however, its advantages and special objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described preferred embodiments of my invention.

Of the drawings:

Fig. 1 is a diagrammatic plan partly Eroken away and in section of a twin muiile iln; Fig. 2 is a section on the line 2-2 of Fig. 1; I

Fig. 3 is a' section on the line 33 of Fig. 1; Fig. 4 is a section through one of the air injection nozzles, the section being taken In the drawings, A represents a kiln having an open kiln chamber with two sets of tracks, B and C, for the kiln cars H, trains of which move along the tracks in the opposite direction, as indicated'by the arrows in Fig. 1. The high temperature zone of the kiln intermediate its ends is heated by closed combustion chambers D located within the kiln chamber, and each having inlet-s D" and D for air and gas, respectively, at one end, and an outlet D for products of combustion at its opposite end. The combustion chambers, as shown, are the type employed in the well known Dressler kiln, and are formed with channels D in their walls, whereby a directed convection current circulation of the kiln atmosphere is set up in the high temperature portion of the kiln. This circulation, and the distribution of the heat through the ware X on the cars H is facilitated by forming transverse channels H in the refractory bodies of the kiln car, ports H preferably being provided which lead from the channels H to the face of the car. platforms on which the goods X are mounted. The cars are provided with flanges H at their sides, which dip into corresponding sand seals I and I and prevent the passage of the highlyv heated kiln atmosphere in the portion of the kiln chamber above the car platforms to the portion of the kiln chamber below the car platforms, to thereby avoid overheating of the metallic umller portions of the cars, and the track rai s.

In so far as above described, the kiln shown in Figs. 1, 2 and 3, contains nothing now novel with me, but on the contrary, is of a type long well known. As the cars H move in opposite directions on the tracks B and C through the kiln, the ware carried by the cars'which are approaching the high temperature zone ofthe kiln, absorb heat from, and thereby cool the ware alongside them on the cars moving away from the high temperature zone of the kiln. The transfer of heat from the hotter ware to the cooler ware is eifected partly by radiation, and artly by a natura convection current circulation of the kilnatmosphere which tends to move upward past the hotter goods to the to of the kiln, thence across the kiln chain r, thence down past the cooler goods, and thence across the kiln to the ower part of the hot side of the kiln as indicated by the arrows'in Fig. 3.

The relatively low thermal conductivit or.

bricks or other ware ordinarily treated in. a tunnel. kiln,'tei1ds to local overheating of the surfaces of the cooler bodies receiving radiant heat and materially restricts the rate at which heat is transferred by radiation. The transfer of heat between the ware and the circulating kiln atmos here is'also e'fiected by the low thermal conductivity of the ware,

An increase in the rate at which heat is transferred from the hotter ware to the cooler ware makes it possible to handle a greater amount of ware in a kiln of given length, or to handle the same amount of ware in a kiln of shorter length than would otherwise be required.

In accordance with the present invention I increase the heat transfer rate from the hotter ware to the cooler ware in the end portions of a twin kiln, by setting up a forced circulation of the kiln atmosphere along paths of flow which loop about the axis of the kiln chamber, the flow being preferably in the same general direction as the kiln atmosphere would move in response to the conditions producing a natural convection current circulation of the kiln atmosphere. I ordinarily effectthis forced circulation by blowing jets of a suitable gaseous medium into the kiln chamber. Each such jet, if properly directed, may be introduced at any point along the looped paths of flow which it is desired to have the kiln atmosphere follow. In practice, however, when the gaseous medium introduced is comparatively'cool, I consider it advantageous to introduce the jets in the more highly heated portions of the kiln chamber, and when the gaseous medium does not absorb, but on the contrary, may add heat to the kiln, the jets are preferably introduced in the cooler portions of the kiln chamber.

In the kiln shown in Figs. 1, 2, and 3, the circulation including means comprises a set of injection nozzles F and a set of injection nozzles G. The injection nozzles F are arranged at intervals along the length of each end portion of the kiln chamber on the hot side of the latter and are arranged to discharge jets of air along the roof .of the kiln chamber from the hotter side of the kiln chamber toward the colder side. As shown each nozzle F is supplied with compressed air under suitable pressure from supply piping F through an individual valved connection F To decrease the number of nozzles required to get a uniform circulation along the length of the kiln chamber in the direction indicated by the arrows in Fig. 3, each nozzle F may be constructed as shown in Fig. l with a discharge orifice manta g or orifices giving a fan-like dischar e. To restrict longitudinal flow through t e kiln chamber, the latter may be divided into lon- F are arranged at the top of the kiln chamher at its underside and discharge downwardly. The gaseous medium discharged by the nozzles G may be preheated air, or may be combustible gas, or a mixture of combustible gas and air sup lied to the'nozy zles through individual v'a ved connections G from a supply pipe G connected through a valve G to a source of gas under pressure and by a valve G to a source of air under pressure. As shown there is one nozzle F and one nozzle G in each section of the kiln between an adjacent pair of nozzles.

The jets discharged by the nozzles F and (1, each tend to set up a circulation of the 1 kiln atmosphere in the same direction in which it would travel as a result of a natural orconvection current circulation if the nozzles were not employed. In a broad way, the nozzles F and G are duplicates, and either set may be used to the exclusion of the other set.- In some cases the nozzles of one set may be used along one portion of the length of the kiln, and the nozzles of the other set along another portion; or nozzles of both sets may be used in one portion of the length ot-the kiln, and nozzles of one set only in the other portions. With the arrangement shown the nozzles G should be supplied with a combustible mixtureof air and gas rather than with combustible gas 'alone when the nozzles Fare not employed, since otherwise there might notbe air in the kiln chamber for the proper combustion of the gas. In lieu of supplying either air or combustible gas or a combustible mixture as the medium for inducing circulation, I may employ any other suitable gaseous medium such as products of combustion. By supplying cold products of combustion through the nozzles F, for exam is,

oxidizing conditions in the kiln chain er would be avoided. As already explained,

the circulation inducing nozzles are not necessarily located as shown in Fig. 3. For example, the nozzles F and G may be replace by nozzles F and G, respectively, located as shown in Fig. 5.

In a mulile heated kiln of the type illustrated in Figs. 1, 2 and 3, provisions should be made for the continuous escape from the kiln of a portion of the kiln atmosphere gases at a rate corresponding to that at which gaseous medium is introduced through the nozzles F and G. The escape of the kiln atmosphere may take place by natural leakage around the doors closing to cause the kiln atmosphere to travel through the end portions of the kiln chamber along helical paths. In some cases the excess kiln atmosphere may advantageously be allowed to escape at the center of the kiln,

as through the damper regulated outlets K, shown or may be allowed to escape part- 1 through the outlets K and partly through the outlet K. Ordinarily when the forced circulation is wholly due to the injection of cold air, the amount of cold air required for the desired circulation with suitable jet apparatus is so small as to involve a small heat loss from the kiln. The use of. cold air increases the cooling rate of the hotter ware, and the amount of circulation inducing cold air employed may be desirably augmented in some cases where especial rapid ware cooling is desired. By regulating the supplies of fluid injected at each nozzle the heat rate of transfer of heat from the hotter to the cooler warecan be correspondingly regulated.

The invention is adapted for use with practically all types of twin kilns. For example, it may be used with advantage with kilns in which the heating gases are carried away from the high temperature zone of the kiln through lines in the portions of the side walls of the kiln adjacent the incoming ware, as in the Anderson Patents No. 3790-10 of March ll, 1888, and No. 37992? of March 26, 1888. in a kiln in which as in the kiln shown in the last mentioned patent, the ware absorbs a portion of the heat which itreceives in the high temperature portion of the kiln, by direct contact with heating gases passing through the kiln chamber, no special roe required, as the excess'portion oil the kiln atmosphere may pass out of the kiln chamber with the heating gases into'the side wall lines which run to the stacks or other draft creating means.

\Vhile. in accordance with the provisions of the statutes, 1 have illustratedand described the best forms of my invention now known to me, it will be apparent to those skilled in the art that many changes in form may be made without departing from the spirit of my invention, and that certain features of my invention may sometimes be employed to advantage'without a corresponding use of other vfeatures. c

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

L'The method of regulating the rate of heat transfer from the hotter ware to the colder ware in the end portion of a. twin tunnel kiln, which consists in setting up a forced circulation of the kiln atmosphere in said portion of the kiln along paths looped about the kiln axis.

2. The method of regulating the rate of heat transfer from the hotter ware to the colder ware in the end portion of a twin tunnel kiln, which consists in setting up a forced circulation of the kiln atmosphere from. the hotter side of the kiln to the colder side in the upper portion of the kiln chamber, and in a reverse direction in the lower portion of the kiln chamber.

3. The method of regulating the rate of heat transfer from the hotter ware to the colder-ware in the end portion of a twin tunnel kiln, which consists in blowing a gaseous medium into said end portion in a direction tending to set up a circulation of the kiln atmosphere along paths looped about the axis of the-kiln.

4. The method of regulating the rate of heat transfer from the hotter ware to the colder ware in the end rtions of a twin tunnel kiln which consists in blowing a gaseous medium into said under portion in a direction tending to set up a circulation of the kiln atmosphere along paths looped about the axis of the kiln and permitting excess kiln atmosphere to escape from the kiln chamber at a point along the length of the kiln remote from that at which the medium is introduced.

5. The combination with a twin tunnel kiln of means for setting up a forced circulation of the kiln atmosphere in an end portion of the kiln along paths looped about the axis of the kiln.

-6. The combination with a twin tunnel kiln of means comprising nozzles for injecting a gaseous medium into the kiln chamber for setting up a forced circulation of the kiln atmosphere in an end portion of the along paths looped about the axis of the neaasae 7. The combination with a twin tunnel kiln of means comprising nozzles for injecting a gaseous medium into the kiln chamber for setting up a forced circulation of the kiln atmosphere in an kiln along paths looped about the axis of the kiln, and means for supplying a combustible fluid to said nozzles.

8. The combination with a twin tunnel kiln of means comprising nozzles for injecting a gaseous medium into the kiln chamber for setting up a forced circulation of the kiln atmosphere in an end portion of the kiln along paths looped about the axis of the kiln, and means for supplying a mixture of gas and air for the combustion of the gas to said nozzles. 9. The combination with a twin'tunnel kiln, of barriers transverse to the length of the kiln chamber fitting closely about the goods pathway through the end portion of said chamber, and nozzles for injecting a gaseous'medium into the sections of the kiln chamber between said barriers to set up a circulation of the kiln atmosphere along paths encircling the kiln axis.

10. The combination with a twin tunnel kiln, ofmeans for injecting a gaseous medium into the end portions of the kiln to set up a circulation of the kiln atmosphere along paths looped about the kiln axis, and means for withdrawing the kiln atmosphere at a regulable rate from the kiln chamber at points displaced longitudinally of the kiln from the first mentioned means.

11. The combination with a twin tunnel kiln of nozzles for injecting fan shaped streams of a gaseous medium into the kiln chamber to set up a forced circulation of the kiln atmosphere along paths looped about the kiln axis.

Signed at Cleveland in the County of Cuyaho a and State of Ohio this Fourth day of one A. D. 1923.

CONRAD DRESSLER.

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